ACT SSC Biology — Unit 3
Speciation — Flashcards & Quiz
Speciation is the formation of new biological species from existing ones through the accumulation of genetic differences and the development of reproductive isolation. ACT SSC Biology Year 12 Unit 3 distinguishes allopatric (geographic isolation) from sympatric (no geographic isolation) speciation and asks you to explain prezygotic and postzygotic isolation mechanisms.
Sample Flashcards
Q1: What is speciation?
Speciation is the formation of new species. It occurs when populations become reproductively isolated and evolve independently through natural selection, genetic drift and mutation until they can no longer interbreed.
Q2: Distinguish allopatric from sympatric speciation.
Allopatric: a geographic barrier physically separates populations. Sympatric: new species arise within the same geographic area through polyploidy, habitat differentiation or behavioural isolation.
Q3: What is reproductive isolation?
Reproductive isolation prevents interbreeding between populations. Pre-zygotic barriers (habitat, temporal, behavioural, mechanical, gametic) prevent mating. Post-zygotic barriers (hybrid inviability, sterility) prevent viable offspring.
Sample Quiz Questions
Q1: Allopatric speciation requires a geographic barrier.
Answer: TRUE
A physical barrier separates populations, preventing gene flow and allowing independent evolution.
Q2: Reproductive isolation is not necessary for speciation.
Answer: FALSE
Reproductive isolation is essential — without it, gene flow prevents populations from diverging into separate species.
Last updated: March 2026 · 3 flashcards · 2 quiz questions